The present invention relates to a sign pen among the so-called "marking pens" and is particularly concerned with an improved sign pen which employs a fine pen tip including very fine tips.
The conventional sign pens are divided into two main classes in structure. One of them has a structure in which a tip member 3a is supported on a shaft tube 1a in a fixed relationship, whereby the projecting length of the top part of the tip member 3a cannot be adjusted or said tip member cannot be removed, as shown in FIG. 1. The other, as shown in FIG. 2 through FIG. 5, includes a structure wherein the protrusion length of the top part of the tip members 3b, 3c, 3d and 3e respectively can be adjusted.
The former sign pen illustrated in FIG. 1 comprises a structure wherein a tip member 3a is inserted through a holding tube 2a secured to the top portion of a shaft tube 1a. The tip member 3a is fixed to the holding tube 2a by means of caulking or the like in such a manner that the top part of the tip member 301a protrudes a desired length from the tube 2a. Thus the tip member 3a is supported to the shaft tube 1 through the holding tube 2a in a fixed relationship, whereby a base part 302a of the tip member 3a fixed to the shaft tube 1a is connected with an ink reservoir member 4a provided within the shaft tube 1a. This is a very popular sign pen that has been widely used for a long time. However, this pen exhibits a disadvantage when using a small-diameter tip for fine writing. In such a case, since the writing pressure is substantially constant regardless of the diameter of the tips, the writing load of the tip per unit area will be increased, causing greater friction between the tip and writing surface (writing surface of paper or similar material) thus the tip will be quickly worn away and become shorter and accordingly its use is materially limited. In order to eliminate this disadvantage, it is desired that the protrusion length of the top part of the tip from the supporting tube be adjustable so as to permit writing with the top portion of the tip having a constant protrusion length at all times, or alternatively providing that the tip can be readily exchanged. However, the sign pen as described above has a structure such that the protrusion length adjustment or exchange of tips is not allowed. Accordingly, it has been strongly demanded to provide an improved structure which permits an adjustment in the protrusion length or the exchanging of tips.
The sign pens illustrated in FIG. 2 through FIG. 5 are provided in order to reply to the above-mentioned demand.
The type of sign pen shown in FIG. 2, which has already been placed on the market as Japanese Utility Model No. 36,529/1972, comprises a structure wherein a head seat member 2b is threadedly engaged with a shaft tube 1b and can be moved axially. However, according to this structure, there are two major problems. First, since a structure to directly contact a tip member 3b with an ink reservoir member 4b within a shaft tube 1b is employed, the tip member 3b, as can be seen in the drawing, reaches the ink reservoir 4b within the shaft tube 1b by means of an axially elongated, axial position adjustable mechanism, i.e., the threaded structure of the shaft tube 1b and the head seat member 2, and therefore a very long tip member is required. With such a long tip member, the ink stored in the ink storage member 4b must flow along a very long passage which may prevent the smooth flow of ink or give rise to a discontinuity in the ink flow. For this reason, a clear marking cannot always be expected. Secondly, in this structure, to directly contact the base part 302b of the tip member 3b with the ink storing member 4b, since said reserving member is made of a member having a fiber structure like a tobacco filter which has a coarse fiber density and much space, the tip member 3b cannot come in contact with the ink reservoir member 4b conveniently and the ink reserved in the said reservoir cannot be properly sucked up by the tip member 3b, resulting in the prevention of a smooth ink flow and a discontinuity of ink. For this reason, a clear marking cannot be obtained.
The latter type of felt pens shown in FIG. 3, FIG. 4 and FIG. 5 have already been placed on the market as the Japanese Utility Model No. 179,248/1979 by the same applicant as the one mentioned before. With each of the structures illustrated in these three drawings, since tip members 3c, 3d, 3e are fixed and supported to their respective shaft tubes 1c, 1d, 1e respectively, even if head seat members 2c, 2d, 2e are respectively threaded with the shaft tubes 1c, 1d, 1e in such a manner as to be able to travel axially, it is difficult to exchange tip members 3c, 3d, 3e when they are worn out. In other words, the structure shown in FIG. 3 comprises: pressing an inner tube 101c having threads into an outer tube 102c and fixing it to the said outer tube to form a shaft tube 1c, mounting an O-ring 103c onto the outer surface front portion of the outer tube 102c, inserting the tip member 3c through a holding tube 4c pressed into and fixed within the inner tube 101c, securing the tip member 3c by caulking the top part of the holding tube, and said head seat member 2c being threadedly engaged with the thread of the inner tube 101c and the base portion thereof being placed over the outer tube 102c to be brought into contact with the O-ring 103c. Accordingly, the tip member 3c is, by means of the supporting tube 4c, fixedly supported to the shaft tube 1c consisting of the inner tube 101c and the outer tube 102c.
The structure shown in FIG. 4 comprises an inner tube 101d having threads therein and pressed into an outer tube 102d and fixed thereto to form a shaft tube 1d, a tip member 3d is inserted through a holding tube 4d which has been pressed into the inner tube 101d and secured thereto, the tip member 3d is fixed by caulking the top part of the holding tube or other similar operation. A head seat member 2d is made up of two divided portions, i.e., a forward segment 201d and a rearward segment 202d, said rearward segment 202d being first engaged with the threads of the inner tube 101d and the base part thereof being placed over the outer tube 102d before said forward segment 201d is threadedly engaged with the threads of the inner tube 101d and thus brought into contact with said rear segment 201d. This is a structure constructed in a so-called double-nut manner or lock-nut manner. Accordingly, the tip member 3d is fixedly supported by way of the supporting tube 4d on the shaft tube 1d consisting of the inner tube 101d and the outer tube 102d.
The structure illustrated in FIG. 5 comprises an inner tube 101e pressed into and fixed to an outer tube 102e to form a shaft tube 1e. A split groove 103e is provided at the top portion of the inner tube 101e so that said inner tube may be springy at the top portion thereof. A tip member 3e is extended through a holding tube 4e pressed into and fixed to said inner tube, the tip member being fixedly secured by means of caulking the top part of the holding tube or other similar operation. A head seat member 2e is mounted on the top portion of the inner tube 101e in such a manner that it can slide in an axial direction. Thus, the tip member 3e is, by means of the holding tube 4e, fixedly supported on the shaft tube 1e consisting of the inner tube 101e and the outer tube 103e.
From the description mentioned above, it can be understood that with any of the structures shon in the above-mentioned three figures, it is very difficult to exchange tip members.
The structure illustrated in FIG. 3 has other disadvantages than the above mentioned disadvantages of nonexchangeability of the tip members: firstly, in this structure, direct contact is established between the tip member 3c and the ink storing member (not shown) within the shaft tube, 1c, which, as in the structure shown in FIG. 2, requires a very long tip member 3c. As a result, the flow of ink may be blocked and thus the ink may be caused to discontinue. Secondly, the ink reserving member is made of a member having the same fiber structure as in FIG. 2, and, therefore, the ink stored in the ink reservoir will not be properly drawn up by the tip member 3c. This prevents the ink from flowing smoothly and causes the ink to flow discontinuously. As a result, a clear marking cannot be expected. Thirdly, since an O-ring 103c mounted on the shaft tube 1c is located adjacent to the base part of the head seat member 2c, it is true that the O-ring 103c substantially abuts against the base part of the head seat member 2c, but the top part of the head seat member 2c may have play around the center line about the O-ring 103c which serves as its fulcrum. This play or unstable condition of the top part of the head seat member will not only produce difficulties in writing but also distort the tip member 3c and prevent the smooth flow of the ink. Thus, the present structure lacks the appropriate considerations for preventing the above-mentioned play.
The structure shown in FIG. 4, in addition to the above-mentioned weak point of non-exchangeability of the tip members, has another disadvantage. In this structure is employed a double-nut system or lock-nut system in which a head seat member 2d consists of a forward segment 201d and a rearward segment 202d, both of said segments being threadedly engaged with an inner tube 101d, and, therefore, in order to adjust the length of the top part of a tip member 3d, said member must be turned successively to travel axially. This means that the present structure is difficult to operate and thus is inconvenient in use.
The structure shown in FIG. 5 includes a split groove 103e at the top portion of an inner tube 101e. Since this split groove is provided in such a position as to be loaded by a head seat member 2d, said top portion may produce a deformation phenomenon through secular change, or, the so-called creep phenomenon, which will result in failing to perform not only functions for chucking or retaining the tip member 3e but also the function for preventing the head seat member 2e from having play or being loose.
Fiinally, it should be kept in mind that the structures illustrated in FIG. 3, FIG. 4, and FIG. 5 have the disadvantage that the smooth flow of ink and the proper holding of ink in the respective tip members 3c, 3d, 3e are prevented. Because the tip members 3c, 3d, 3e shown in the three figures are respectively supported by means of caulking of the holding tubes 4c, 4d, 4e, the flow passage of ink will be pressed to become narrower, so that the smooth ink flow will be prevented and the proper retaining of ink cannot be established. Accordingly, clear writing cannot be expected.
Accordingly, the present invention has been devised in order to eliminate the above-mentioned disadvantages present in the prior art, well known sign pens. The present invention is characterized in that the head seat member is adapted to be threadedly engaged with the shaft tube, whereby the tip member can be exchanged and the extrusion length of the top part of the tip member can be adjusted. On the outer surface of the engaging tube of the head seat member is arranged a projection structure abutting against the top portion of the inner surface of the shaft tube thereby preventing the head seat member from becoming loose under pressure applied from any direction during marking. In said head seat member the engaging tube is provided with one or more axially elongated slit(s) extending substantially to the end thereof so that said engaging tube is adapted to be deformed by means of said slit, the deformation preventing said engaging tube from engaging the shaft tube too tightly, thereby permitting the smooth axial movement of the head seat member and the easy fine adjustment of the extrusion length of the tip member top part. Within the shaft tube is fixed an ink guide core communicating with an ink reservoir provided within the shaft tube. The tip member is connected with the said guide core, eliminating the use of a very long tip member for smooth ink flow and thus for clear marking. Furthermore, the marking pressure applied on the tip member is received by said ink guide core in order to prevent deformation or destruction of the top member. In the form of a conical surface is arranged the top portion of a small-diameter central opening adaptable to the diameter of the tip member. Over the front portion of the ink guide core is fixedly positioned a collector of the -type section, in which a large-diameter opening adaptable to the diameter of the ink guide core is provided at the base part side of the central opening opposite said conical surface, whereby said collector prevents the ink guide core from being broken into pieces or being cut apart due to marking pressure or similar cause. As a result, it is easier to collect ink in the front part of the ink guide core, as well as when communicating the tip member with the ink guide core, such communication being readily achieved and correctly by means of the conical surface so that the tip member is prevented from being deformed or being destroyed at the base portion thereof. The ink in the ink guide core is allowed to flow smoothly into the tip member, and said collector prevents the ink stored in the top portion of the ink guide core from evaporating or drying unnecessarily. Through the collector extends the base part of the tip member protruding from the head seat member for communicating with the ink guide core, whereby, without fixing the tip member anywhere, the collector can support the tip member to the degree that the tip member can maintain its immovable state against, the axial movement of the head seat member oscillation or shock in order to prevent the ink flow passage within the tip member from narrowing due to the fixed engagement of the tip member, as well as to permit easy and quick exchange of the tip member.
Accordingly, the main object of the present invention is to provide an improved, high-quality and useful marking pen which can eliminate all of the disadvantages included in the prior arts.